Turns out, being obese isn’t necessarily a bad thing. In a new study by U.S. and European researchers, published [PDF] in the European Heart Journal, overweight and obese people were found to be at no greater risk of developing or dying from heart disease or cancer, compared with normal weight people, as long as they were metabolically fit despite their excess weight.

The researchers examined data on 43,265 participants enrolled in the Aerobics Center Longitudinal Study between 1979 and 2003, who filled out questionnaires about their lifestyle and medical history and also underwent physical exams, blood tests and a treadmill test to gauge their cardiovascular fitness. The researchers categorized obese participants as “metabolically healthy” if, aside from their weight, they didn’t suffer from insulin resistance, diabetes, low levels of good cholesterol, high triglycerides and high blood pressure. Nearly half of the obese participants in the study qualified as metabolically fit.

Compared with obese people who had at least two of the above markers of poor health, those who were obese but metabolically healthy had a 38% lower risk of early death from any cause. In fact, those who were fat but fit had no higher death risk than metabolically healthy normal weight participants.

The finding runs counter to the prevailing wisdom that weight is in and of itself a marker of health; rather, it suggests that a person’s level of physical fitness, in addition to his or her weight, matters too. “Weight is a major issue when it’s combined with a metabolic abnormality,” says study co-author Dr. Timothy Church, director of the Laboratory of Preventive Medicine at Pennington Biomedical Research Center in Baton Rouge. “When you have weight plus insulin resistance, weight plus hypertension, weight plus abnormal cholesterol — then you have an issue. Obviously the more overweight and the more obese you are, the more likely you are to have a metabolic abnormality.”

The new paper falls in line with other recently released research, including a study presented last week at the European Society of Cardiology meeting that was based on 14 years of data from a Centers for Disease Control and Prevention survey. That study found that, when it comes to your risk of early death, being obese overall may not be as important as where on the body your fat is distributed. In the study, people who were of normal weight but had a paunch — that is, a lot of visceral or belly fat, which, unlike run-of-the-mill subcutaneous fat, is known to be metabolically dangerous and to promote insulin resistance and inflammation — were twice as likely to die early as people of normal weight with no gut. People with lots of concentrated belly fat also had a higher risk of death than people who were simply obese all over.

Another study published in the Journal of the American Medical Association in early August added evidence for the so-called obesity paradox, finding that among people already diagnosed with Type 2 diabetes, those who were obese lived longer than their thinner peers. Similarly, in a second study published in the current issue of the European Heart Journal, researchers looked at nearly 65,000 patients with heart disease and found that overweight and obese people had the lowest risk of early death, compared with normal-weight or underweight patients; those who were underweight had the highest death risk.

So what exactly is going on? Being metabolically fit may be the game changer, says Church, and physical fitness — irrespective of weight — is a strong predictor of whether or not you’re going to be metabolically fit. “Think about insulin resistance. The biggest consumer of sugar in the human body is muscle. Muscle doesn’t just move us from point A to point B; it is also extremely important for many metabolic variables like blood sugar,” says Church. “So it makes sense that someone who is fit is metabolically going to be far better off than someone who is unfit.”

That’s why some heavy people can be fit on the inside — healthier even than some of their thinner peers. Many people who diet but don’t exercise to lose weight, for example, may technically reach a “healthy” weight, but their fitness level doesn’t match. They may appear trim on the outside, but still carry too much visceral fat and not enough muscle on the inside. “They’re not physically active. They have horrible and restrictive diets. They might not be overweight, but metabolically they’re a mess,” says Church.

The key is what doctors and public health experts have been saying all along: get more exercise — whether you’re thin or fat. “Based on the data that our group and others have collected…we believe that getting more exercise broadly and positively influences major body systems and organs and consequently contributes to make someone metabolically healthier, including obese people,” said Francisco Ortega, lead author of the first European Heart Journal paper and a research associate at the University of Granada in Spain, in a statement.

“You have to remember it doesn’t take that much to be fit,” says Church. “To qualify as fit, it takes about 30 minutes of walking five days a week on average. That’s not a ton of caloric expenditure. It is actually quite easy physiologically to be overweight or obese, but also qualify as physically fit.” Federal guidelines recommend at least 2.5 hours of moderate-intensity aerobic exercise a week.

The bottom line is that the new findings aren’t an excuse to remain overweight or obese: although research increasingly suggests that excess weight alone may not necessarily lead to disease or early death, you’re still more likely to develop other metabolic risk factors that contribute to chronic disease if you’re overweight.